onsemi MMBT4400

Overview

MMBT4400 from Fairchild Semiconductor is an NPN general-purpose amplifier and switch rated for continuous collector current up to 600 mA, with V_CEO = 40 V, V_CBO = 60 V, and V_EBO = 6.0 V, optimized for low-to-moderate power switching and linear amplification in consumer and industrial control circuits.

For engineers reviewing the MMBT4400 datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain (h_FE = 20–150 at I_C = 1–500 mA), saturation voltages (V_CE(sat) ≤ 0.75 V at I_C = 500 mA), thermal resistance (R_θJA = 357 °C/W), and SOT-23 package compatibility in space-constrained PCB layouts.

Technical Context

The MMBT4400 operates as a silicon NPN bipolar junction transistor with fixed-emitter configuration, supporting both analog amplification (h_fe = 2.0 at f = 100 MHz, I_C = 20 mA) and digital switching (t_d = 15 ns, t_s = 225 ns at V_CC = 30 V). Its junction temperature range spans −55°C to +150°C, enabling use in extended-temperature environments.

It exhibits low output capacitance (C_ob = 6.5 pF at V_CB = 5 V) and input impedance (h_ie = 0.5–7.5 kΩ at f = 1 kHz), supporting stable small-signal performance across audio and low-MHz switching frequencies without external compensation.

Key Specifications

Pinout & Package

SOT-23 plastic surface-mount package (marking code: "83"), with standard pin assignment: Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector. Designed for reflow-compatible assembly and thermal relief via PCB copper pour under exposed pad (if present per variant).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN switching and amplification applications.

Compared with PN2222A and MPSA42, the MMBT4400 offers the best balance of SOT-23 footprint, 600 mA current capability, and 40 V breakdown for cost-sensitive, space-constrained switching-making it ideal for consumer-grade power management where voltage margin and thermal headroom are tightly bounded.

Availability

MMBT4400 is available at Aetrix Electronics and suitable for LED driver circuits, microcontroller GPIO expansion, and DC motor speed control requiring stable component supply and consistent parametric performance across production batches.

Supply support for MMBT4400 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, signal conditioning, and discrete components before its acquisition by ON Semiconductor in 2016.

The MMBT4400 belongs to Fairchild's general-purpose bipolar transistor family, engineered for robust, low-cost switching and amplification in high-volume consumer and industrial electronics where reliability and manufacturability are prioritized over ultra-high-speed or precision analog performance.

FAQ

What is the maximum continuous collector current rating for the MMBT4400?

The MMBT4400 is rated for 600 mA of continuous collector current (I_C) at T_A = 25°C. Derating applies above 25°C per the specified 2.8 mW/°C slope. This rating defines the upper limit for sustained load switching or linear operation without exceeding thermal limits in the SOT-23 package. The MMBT4400 must be operated within this boundary to maintain reliability and avoid junction overheating.

Is the MMBT4400 pin-compatible with the 2N4400?

No-the MMBT4400 uses the SOT-23 surface-mount package (pinout: E-B-C), while the 2N4400 uses the TO-92 through-hole package (pinout: E-B-C but physically incompatible). Though electrically similar, they are not mechanically interchangeable. The MMBT4400 requires SMT assembly and layout; substituting it for a 2N4400 demands PCB redesign. The MMBT4400 is not a drop-in replacement for the 2N4400.

What is the typical DC current gain (h_FE) of the MMBT4400 at 150 mA collector current?

At I_C = 150 mA, V_CE = 1.0 V, and T_A = 25°C, the MMBT4400 exhibits h_FE = 50 (minimum) to 150 (maximum), with typical value near 100. This gain range determines base drive current needed for saturation-e.g., ~1.5 mA base current ensures full turn-on at 150 mA collector load. The MMBT4400's h_FE remains usable across its full current range, supporting both switching and linear modes.

Can the MMBT4400 be used in audio amplifier applications?

Yes-the MMBT4400 supports audio-frequency amplification with h_fe ≥ 20 at 100 MHz and h_ie = 0.5–7.5 kΩ at 1 kHz, enabling stable common-emitter gain stages for microphone preamps or line drivers. Its low noise and predictable gain variation across temperature make it suitable for non-critical audio paths. However, the MMBT4400 is not optimized for ultra-low-noise or high-fidelity applications; dedicated low-noise transistors are preferred for sensitive front-end stages.

What is the thermal resistance junction-to-ambient (R_θJA) for the MMBT4400 in SOT-23?

The MMBT4400 has R_θJA = 357 °C/W in the standard SOT-23 package, measured under JEDEC JESD51-2 conditions on a 1-inch² FR-4 board with 2 oz copper. This value governs allowable power dissipation: at 25°C ambient, max P_D = 350 mW; at 70°C ambient, it drops to ~215 mW. Proper PCB copper area under the tab (if applicable) and airflow improve actual thermal performance. The MMBT4400's R_θJA reflects its suitability for low-power, naturally cooled applications.